Films of thermoplastic polymer compositions have found many commercial uses, particularly in packaging. One use of such films is in the production of shrink films and films for wrapping foods.
Blown films are popular in the commercial arena. Methods for producing blown film from commercial film grade polybutylene resins are described in Technical Bulletin SC:397-79 of Shell Chemical Company, "Processing Shell Polybutylene Film Grade Resins," published May 1979.
The present invention relates to compositions which can be formed into films or sheets that have improved processing properties and good optics. The novel sheets can be biaxially oriented to result in films with good optics. The present invention aids in reducing the number of scraps which result from making films with a biaxially stretched system. The present invention also relates to blown articles with high gloss and clarity container when compared with more conventional low melt index butene-1 polymer blends.
Finally, the present invention relates to fibers which have improved stretchability, and are capable of being spun because it is believed that the high melt index butene-1 polymers act as a lubricant or plasticizer for the essentially propylene fibers.
U.S. Pat. No. 3,808,304 issued to Schirmer discloses heat sealable blends of butene-1 homopolymer with polypropylene. Schirmer does not discuss using melt index butene-1 polymers prepared by peroxide cracking as in the present invention. In addition, Schirmer discloses that preferred blend use polypropylene at levels of 20-80% by weight.
U.S. Pat. No. 4,075,290 issued to Denzel discloses heat sealable blends of 80-99% by weight of polybutylene and 1-20% by weight of polypropylene. The disclosure is limited to specified ranges of each polymer component.
U.S. Pat. No. 4,354,004 issued to Hughes claims a heat sealable blend prepared from butene-1-ethylene copolymers, about 2-9% by weight of polypropylene and from about 0.02% to 1.5% by weight of high density polyethylene.
U.S. Pat. No. 3,455,871 issued to Coover, assigned to Eastman Kodak Co. describes substantially crystalline homopolymer and copolymers of 1-butene as a concentrate carrier for non-olefinic additives. The Coover patent does not claim or describe the same kind of material as used in the present invention. Coover claims a butene-1 material with an intrinsic viscosity in the range of 0.2 to 5.0. The present invention has properties different from the Coover material.